This invention relates to methods and apparatus for washing, etching, rinsing, and plating substrates including electroless plating and electroplating.
In particular, magnetic disks are typically made of an aluminum alloy substrate having an electroless or electrodeposited nickel plate intermediate layer and a surface layer of magnetic read/write material sputtered onto the nickel plate. The nickel plating process involves submersing and agitating the aluminum alloy substrate in a plating bath to electroless plate a nickel-phosphorus alloy layer onto the substrate. Thereafter, the plated substrate may be polished and textured, and one or more underlayers, one or more magnetic layers, and one or more protective overcoats are deposited (e.g. by sputtering) onto the plated substrate.
There are various manufacturing processes utilized for plating substrates. For example, during some processes for making magnetic disks, the disks must be washed, rinsed, plated, and etched clean of foreign contamination of various types. Some of the fluids that are used are caustic and/or harmful to an operator which precludes manual handling during some or all steps of the washing, rinsing, plating or etching process.
For example, in one process, one first submerses, agitates, and soaks substrates in an alkaline cleaner (e.g. a KOH solution plus an inhibitor) in a first tank. Then one rinses the substrates by submersion, agitation, and soaking in a second tank. Next one submerses, agitates, and soaks the substrates in an acidic solution (e.g. phosphoric acid) in a third tank. Next one again rinses the substrates by submersion, agitation, and soaking in the second tank. Finally, the substrates are placed in a plating bath in a fourth tank. This plating bath comprises the chemicals used to plate a nickel-phosphorus alloy (NiP), e.g. nickel sulfates, sodium hypophosphite and chelating agents. The nickel plating chemistry can be a type 300 ADP, manufactured by Enthone Corp. Other plating chemistries are available from OMG Chemistries.
To implement the above processes, it is necessary to move the substrates between four separate tanks. To accomplish this, an entire plating rack and rotatable carousel may be transported between the four separate tanks. Such transportable, immersible, rotatable carousels for washing, etching, rinsing and plating substrates are known in the art.
An apparatus for immersing articles in a violently agitating electroplating bath has been described in detail in U.S. Pat. No. 4,516,523. The apparatus is capable of being immersed in a liquid bath and supports at least two dowels or rods on which are mounted apertured disks in a spaced apart relationship. Each dowel or rod has a gear fixed near one end and has a plurality of axially spaced circumferential grooves in each of which respective apertured disks are disposed. A pair of spaced wheels are provided to rotate in unison about a fixed central axle. Each wheel has a plurality of radially disposed slots into which respective dowels or rods are disposed so that each dowel continuously rotates about its own axis. The central axle supports a fixed sun gear disposed near one wheel and each rod has at one end a planet gear that meshes with the sun gear whenever the respective dowel or rod is nested within a respective pair of slots on the wheels. A motor and a corresponding gear assembly is provided to continuously rotate the pair of wheels and the at least two dowels about the central axle and continuously rotate the at least two dowels or rods about their own axis. However, U.S. Pat. No. 4,516,523 does not describe a continuous rotation of the disks about a central axis and a selective rotation of the disks about their own axis.
Although the apparatus shown and described in U.S. Pat. No. 4,516,523 is generally suitable for electroplating substrates, the apparatus is not shown to be versatile enough to provide optimal performance for each of the washing, etching, rinsing and plating process steps. In particular, the current inventors have found that the ability to provide a continuous rotation of the substrates about a central axis and a selective rotation of the substrates about their own axis allows optimization of the washing, etching, rinsing and plating process steps.
What is needed in the industry is a transportable, immersible, variably-rotatable apparatus that is movable between multiple process tanks and that is capable of providing a continuous rotation of the substrates about a central axis and a selective rotation of the substrates about their own axis which allows optimization of various washing, etching, rinsing and plating process steps.